How to prevent stealing of rails?

I am planning to build a railway from frontier soouth (SMP5) far to S and E (~ 22.000 rails). However, lately a lot of rails were stolen from the railway I built to get to my home in the NW (I used to connect to already existing railways whenever possible, and the were also raided). I wonder if there is a way to prevent this type of griefing. Would it be useful to take automatic screenshots of the dynmap every minute or so, or are there less clumsy tricks?

Cant do much for prevention yet, but we are able to track more blocks now if they are recently placed (In other words: If you built something more than a month ago, replace the blocks so they can be tracked)

One thing that helps, of course, is hiding the rails. Do this by starting the rail away from a spawn area and either really far down or, if in the nether, really far up. This discourages it by making it harder to find thus less likely a lazy griefer will run into it.

Taking screenshots of the live map probably won't help simply because you can hide from the live map.